Device to determine effective pulmonary blood flow
First Claim
1. Arrangement for the determination of the effective pulmonary blood flow by means of partial CO2 rebreathing wherebythe line from the endotracheal tube of the patient (tube) to the respirator between a controllable 3-way valve (4) and a Y-fitting (5) is split into two branches,one branch forms a bigger dead space (6) for the CO2 rebreathing whereby for measurement of the CO2 elimination and expiration termination CO2 partial pressure a CO2 sensor (3) and a respiratory flow sensor (1) at the endotracheal tube of the patient and for calculation of the effective pulmonary blood flow a microprocessor/controller (7) is provided,the switching between the two branches is carried out by the 3-way valve (4) that can be controlled through the microprocessor/controller (7),the calculation of the effective pulmonary blood flow is performed using the equation ##EQU2## whereby VCO2 (NR) is the CO2 elimination (ml/min) during the nonrebreathing period measured as the mean value of the CO2 elimination of complete respirations within 60 s until immediately before the beginning of the rebreathing period,PetCO2 (NR) is the expiration termination CO2 partial pressure (kPa) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO2 partial pressures of complete respirations within 60 s until immediately before the beginning of the rebreathing period,VCO2 (R) is the CO2 elimination (ml/min) during the rebreathing period measured as the mean value of the CO2 elimination of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way valve (4) into the rebreathing position),PetCO2 (R) is the expiration termination CO2 partial pressure (kPa) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO2 partial pressures of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way valve (4) into the rebreathing position),Fs is a scale factor for the representation of the effective pulmonary blood flow in l/min with Fs=10,PBF is the effective pulmonary blood flow (l/min) wherebyf(PetCO2 (R), PetCO2 (NR), Hb) is the standardised CO2 dissociation curve in blood.
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Accused Products
Abstract
The invention relates to a device to determine effective pulmonary blood flow (PBF) by means of partial CO2 rebreathing. The device is characterized in that it comprises an endotracheal tube whose conduit leading from the patient to the respirator is divided up into two lanes between a controllable three-way valve (4) and a Y-piece; one lane builds a larger dead area (6) for CO2 rebreathing whereby, in order to measure CO2 elimination and end expiratory partial CO2 pressure a CO2 sensor (3) and a respiration flow sensor (1) are provided on the endotracheal tube of the patient. The calculation of effective pulmonary blood flow is provided by a microprocessor/controller (7) which also controls the three-way valve (4) which provides the switching between both lanes.
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Citations
2 Claims
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1. Arrangement for the determination of the effective pulmonary blood flow by means of partial CO2 rebreathing whereby
the line from the endotracheal tube of the patient (tube) to the respirator between a controllable 3-way valve (4) and a Y-fitting (5) is split into two branches, one branch forms a bigger dead space (6) for the CO2 rebreathing whereby for measurement of the CO2 elimination and expiration termination CO2 partial pressure a CO2 sensor (3) and a respiratory flow sensor (1) at the endotracheal tube of the patient and for calculation of the effective pulmonary blood flow a microprocessor/controller (7) is provided, the switching between the two branches is carried out by the 3-way valve (4) that can be controlled through the microprocessor/controller (7), the calculation of the effective pulmonary blood flow is performed using the equation ##EQU2## whereby VCO2 (NR) is the CO2 elimination (ml/min) during the nonrebreathing period measured as the mean value of the CO2 elimination of complete respirations within 60 s until immediately before the beginning of the rebreathing period, PetCO2 (NR) is the expiration termination CO2 partial pressure (kPa) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO2 partial pressures of complete respirations within 60 s until immediately before the beginning of the rebreathing period, VCO2 (R) is the CO2 elimination (ml/min) during the rebreathing period measured as the mean value of the CO2 elimination of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way valve (4) into the rebreathing position), PetCO2 (R) is the expiration termination CO2 partial pressure (kPa) in the respiratory air during the rebreathing period measured as the mean value of the expiration termination CO2 partial pressures of complete respirations within 15 to 30 s after the patient has begun to be respired through the big dead space (6) (after switching the 3-way valve (4) into the rebreathing position), Fs is a scale factor for the representation of the effective pulmonary blood flow in l/min with Fs=10, PBF is the effective pulmonary blood flow (l/min) whereby f(PetCO2 (R), PetCO2 (NR), Hb) is the standardised CO2 dissociation curve in blood.
Specification